Heat treating apparatus



March 24, 1942. 5 DENNEEN ET AL 2,277,082

HEAT TREATING APPARATUS Filed March 28, 1939 4/ V 4 W A 3 FIGZ.

INVENTOR, FRANCIS S. DENNEEN AT TOR NEYS Patented Mari 24, 1942 HEAT TREATING APPARATUS Francis S. Dcnneen, Cleveland, and William C. Dunn, Shaker Heights, Ohio, asslgnors to The Ohio Crankshaft Company, Cleveland, Qhio, a

corporation of Ohio Original application August 19, 1935, Serial No. 36,842. Divided anal this application March 23, 1939, Serial No. 2645MB I Claims.

The present invention is a division of our co= pending application Serial No. 36,842, filed August 19, 1935, and relating to heat treated metallic surfaces. The instant invention is particularly directed to an apparatus by which heat treated surfaces on gears and. the lilre may be attained.

In the heat treatment of metals generally and in the hardening of ferrous metals in particular, there have been no teachings which would sh able those skilled in the art to produce hardened zones of metal of predetermined characteristics as to depth and general contour on articles having abrupt or irregular changes in surface form by the use of electric heat. Surface harder-line processes used heretofore were not adapted. to the hardening of such surfaces as the contacting surfaces of gear teeth or splines, the side walls oi" sliding lreys and lzeyways, the rifled interiors of gun bores, and many other similar surfaces. In the hardening of surfaces such as those above enumerated, it is often important that adjacent surfaces as well as the core or metal under the surface, be kept softer in order that it be sum ciently ductile to resist fractures clue to shock, vibrations ancl other causes. For instance, in a gear tooth, the addendum surf aces should be harol in order to resist the abrasion of sliding and rolling contact of other tooth surfaces, while the metal in the dedenuum and at the root of the tooth which does not contact with any wearing or abrasive element, but which is submitted to heavy bending stresses due to the cantilever construction of gear teeth, should remain stro and. comparatively ductile to prevent breakage or the formation of incipient fractures. Expo rience has taught that brittleness in steel usually increases with hardness, and. the greater the britttleness the more the metal is susceptible to the formation of surface cracks or incipient fractures which eventually extend far enough into the metal to cause complete failure of the section aiiected. B

Our apparatus is applicable not only to gears, but to numerous other articles as hereinafter explained, such as spline-:1 shafts, reamers, drills, gun bores, the wearing surface of pulverizing and crushing machines, friction feed rolls and the like, and to almost any metal article requiring a hardened zone, particularly where there is an uneven surface. 1

With the aforementioned conditions in view, this invention then has as its chief object the provision of an apparatus whereby the wearing surfaces of a gear may be hardened without detrimental changes affecting other parts of the gear. Another object is to provide an apparatus whereby the addendum portions or all teeth may be hardened simultaneously and uniformly. Numerous other objects will become apparent from the following description in which details of apparatus capable of producing improvecl results will be defined and new and advantageous steps in the procedure for obtaining such results will be described or suggested to those slrlllecl in the art of heat treating.

Fig. l is a longitudinal section illustrating means for heating and quenching gear teeth;

and.

Fig. 2 is a section tal-icn on line JET-ll of Fig. l.

While in most cases the preferred method. oi heating is by high frequency induced currents set up in the zones to be hardened, the heating may also be accomplished by the direct flow or" current into the article through electrical con taccs established between the article and parts of the apparatus.

Referring now to the drawing, we show one form. of apparatus for accomplishing the results of our invention. In this apparatus the gear ill to be hardened is non-rotatably mounted. on the arbor El which is supported in, but insulated at 222 from the cover member The conductor unit is supported loo-axially with the gear so. This conductor unit has one or more axially extending conductor bars and it formed to pass between adjacent teeth of the gear it and in suitably spaced relationship thereto.

Terminals :from a source of high frequency current are connected at 2i and 28. This high frequency current is thus caused to flow through the bars 25 and t6 and in so doing induces heating currents in the surface zones of the tooth faces which are in proximity with these bars. An enclosure shell 29 surrounds the space occupied by the gear and is insulated from the conductor bars by rings 30 and 3 I.

Immediately upon attaining a sufiiciently high temperature, a quenching fluid supplied through pipe fittings connected at 32 and 33 is vigorously projected into the enclosure, completely flooding and quenching the heated surfaces, passages such as 34 allowing the cooling fluid to escape. After suflicient cooling, the flow of quench is interrupted, and the cover 23 carrying the arbor 2| and gear 20 is retracted sufliciently to clear the ends of the conductors and is then rotated to bring the conductors into line with the next pair of tooth spaces. The cover 23 and gear 20 are then reinserted and the operation repeated, thus hardeningthe faces of the adjacent teeth. It will be evident that a continuation of these repeated operations will harden the surfaces of all teeth.

By increasing the number of conductor bars several teeth may be hardened simultaneously and with small gears, or with larger gears where sufncient heating energy is available, enough conductor bars may be used to heat all the teeth at one time.. The conductor bars will be so formed and the current supply so regulated as to equalize the heating of the several teeth. 7

For some purposes, substantially the same apparatus last described is used with low frequency accomplished while the conductor bars are still in the heating position, the conductor bars and the tooth surfaces being quenched at the same time.

Obviously, however, means may be readily provided for retracting or withdrawing the conductor unit 24 with its attached conductor bars 25 and 26 by quickly withdrawing this assembly from its position within the enclosure by means of a spring or quick acting lever attached to the shaftprojecting portion of the member 24. with the conductors removed from between the gear teeth, the heated tooth surfaces may be quickly and vigorously quenched.

Other forms may be employed embodying the features of our invention instead of the one heree in explained, change being made as regards th'e means. and the steps herein disclosed, provided the elements stated by any of the following claims or the equivalent of such stated elements be employed, whether produced by my preferred method or by others embodying steps equivalent to those stated in the following claims.

We therefore particularly point out and distinctly claim as our invention:

1. In apparatus of the character described for heating gears and the like, a substantially cuplike element having a projection interiorly thereof so that a gear may be inserted in said element with said projection extending between adjacent teeth thereof, a rotatable electrical conducting cap in communication with said projection for sealing said cup, an arbor carried by said cap and adapted for supporting a gear in heating relation with said projection, said cap having openings therein in registration with said cup, means for supplying quench interiorly of said cup for quenching said gear so that the quench may exit by means of said openings and electrical lead-ins one in communication with said element and the other in communication with said cap.

2. Th combination of a cup-like element adapted for receiving a gear interiorly thereof and having a projection adapted for lying 'between adjacent teeth of said gear, rotatable and reciprocable means for supporting said gear in heating relation with said element and for sealing said element, said means having an opening therein in communication with the interior of said cup-like element, an electrical lead-in in communication with said cup-like element, an

' lik'e element whereby the spent quench may exit through said opening.

3. In apparatus of the character described for heating gears and the like, means presenting a surface having circumferentially spaced conductor bars extending therefrom, a shell insulated and spaced from said conductor bars whereby there is provided substantially a cup-like formation having a passageway communicating with and between said conducting bars, means for admitting quenching fluid to said passageway, means for supporting a gear within said cuplike formation so that said bars are disposed between adjacent teeth of said gear, and means for passing an electrical h'eating current through said conductor bars whereby said teeth are heated.

4. In apparatus of the character described for heating gears and the like, a substantially cuplike element having a projection interiorly thereof so that a gear may be inserted in said element with said projection extending between adjacent teeth of said gear, an electrical conducting cap element in communication with said projection for sealing said cup, means insulated from said cap element for supporting a gear with said projection extending between adjacent teeth thereof, one of said elements being rotatable relatively to the other, means for supplying quench interiorly of said cup-like element for quenching said gear and electrical lead-ins one in communication with each of said elements.

5. In apparatus of the character described for heating gears and the like, means presenting a substantially cup-like open end formation, means disposed interiorly of said formation for heating a gear, means for supplying a quenching fluid interiorly of said formation for quenching a gear, and cover means for covering said open end and for supporting a gear in heating relation with said heating means, said cover means being provided with openings in communication with the interior of said formation whereby the spent quench may exit through said openings.

6. In apparatus of the character described for heating gears and the like a substantially cupshaped conductor unit having a plurality of conductor bars, a cover member for sealing said conductor unit, means carried by said cover member for supporting a gear coaxially with said conductor unit so as to have the gear teeth in heating relation to the conductor bars, said cover member having openings in registration with the cup-shaped conductor both for admitting a cool-.

ant to quench the gear and for draining it thereafter, and electrical lead-ins, one connected to the conductor and the other to the cover member.

7. In apparatus of the character described for heating gears and the like a substantially cupshaped conductor unit having a plurality of conductor bars, a cover member for sealing said conductor unit, means carried by said cover member for supporting a gear coaxially with said conductor unit so as to have the gear teeth in heating relation to the conductor bars, means for quickly withdrawing and returning respectively said gear out of and into the heating relation with the conductor bars, means for moving the gear progressively so as to prepare the next set of teeth for cooperation with the heating means, means for quenching the heated portions, and

lead-ins for connecting the conductor and the cover with a source of high frequencycurrent.

8. In apparatus for heating gears and the like, a formation substantially in the shape 01' a cup, a conductor bar extending axially in said cup, a cover for said cup, means for supporting a gear in the cup, the bar being disposed to extend between adjacent teeth of the gear, means for supplying current to the conductor bar to heat the teeth, a shell comprising a part of the cup, the shell being insulated from other parts of the cup, and means for passing fluid through a wall of the shell to cool the bar and the gear.

- 9. In apparatus for heating gears and the like. acylindrical shell, a closure member at each end of said shell, said shell and said closure members members, members for supporting a gear in the shell, the conductor-bar being disposed to lie between adjacent teeth or the gear, and terminals for connecting the closure members to a source of heating current to flow the current through the conductor bar to heat the teeth of the gear.

10. In apparatus for heating adjacent projections on a metallic article, a substantially cylindrical shell, a closure member at each end of said shell to form a closed conductor unit with said shell, a conductor bar extending axially in the shell, the bar being supported by the closure members, means for supporting the metallic article in the shell, the-conductor bar being disposed to lie between the adjacent projections on the metallic article, and means for supplying heating current to the conductor bar to heat the projections.

FRANCIS S. DENNEEN.

WILLIAM C. DUNN. 

